The present invention relates to a method and apparatus for manufacturing a cathode ray tube, wherein a neck portion of a bulb of the cathode ray tube and a stem of an electron gun inserted in the neck portion are welded.
Steps of manufacturing a cathode ray tube include a step of sealing a cathode ray tube bulb. In the sealing step, an electron gun is inserted at a predetermined position in a neck portion of the bulb with a high positional precision, and then a stem of the electron gun and the neck portion are externally heated by a burner and integrally welded.
As a method for practicing this welding, the following method is known. More specifically, an electron gun is inserted in a neck portion of a bulb. Then, the entire assembly is rotated about the neck portion, and the neck portion is heated by the flames of burners provided on two sides of the neck portion, thereby welding the neck portion and the stem of the electron gun.
According to another known welding method, an electron gun is inserted in a neck portion of a bulb, burners provided on two sides of the neck portion are rotated along the outer surface of the neck portion, and the neck portion is heated by the flames of the burners, thereby welding the neck portion and the stem of the electron gun.
In the former method, however, since the bulb and the electron gun are rotated, an oscillation caused by the rotation occurs in the bulb. This oscillation may cause off-centering of the electron gun and the neck portion of the bulb, or the electron gun may contact and damage the phosphor layer of the bulb. As a result, sealing precision of the bulb is degraded.
In the latter method, since a plurality of burners are rotated, problems are caused by oscillation as in the former method, and a complex mechanism is required for rotating the burners.